I’ve been reading and thinking a lot lately about the process of aging. Many scientists who study it argue — quite convincingly — that it’s the most important scientific topic of our time. In his 1997 bestseller Time of Our Lives, biological gerontologist Tom Kirkwood writes that the science of human aging is “one of the last great mysteries of the living world.”
Over the past century, Kirkwood notes, developed countries have used preventative and offensive tactics to slash infant mortality, smoking, and accident rates, and to conquer most infections. In the 1880s, the top causes of death were respiratory diseases (like tuberculosis and influenza) and digestive diseases (like cholera and typhoid), and life expectancy was around 46 years. Today, we’re living three decades longer and dying of illnesses — such as cancer, stroke, and dementia — that most of our ancestors didn’t grow old enough to get.
Perhaps because people are living longer and longer, we tend to think about aging as a modern phenomenon. “Data from the Census Bureau tell us that there are currently around 39 million Americans age 65 and older, up from 25.5 million just 30 years ago,” notes the website of the National Institute on Aging. “This population explosion is unprecedented in history, and the resulting demographic shift is causing profound social and economic changes.”
Though it may be getting a surge of scientific and cultural attention, aging isn’t a new problem. Far from it: Philosophers have been fretting over old age for thousands of years, asking essentially the same thorny, metaphysical questions that get asked today. This became obvious to me this weekend while reading The Nature of Man, a fascinating and surprisingly eloquent book published in 1903 by Russian biologist Élie Metchnikoff.
The book’s basic premise — that science and reason can lead to optimism and happiness, despite religious arguments to the contrary — is interesting in its own right. And I’ll get into how it relates to aging. But Metchnikoff’s argument is even more interesting if you know a bit about his personal life.
When he was 18 years old, Metchnikoff married a woman with tuberculosis. She was sick enough on their wedding day to be carried to the church, and stayed sick for the next decade before dying in 1873. Devastated, Metchnikoff tried to kill himself with an opiate overdose. He married again in 1875, and five years after that his second wife caught typhoid fever. She almost died, and Metchnikoff again attempted suicide.
Metchnikoff’s depression lifted in 1883 with the discovery that would make him famous (and later earn him the Nobel Prize). He was the first to identify phagocytes, cells of the immune system that engulf and destroy invading microbes. He became friendly with Louis Pasteur, whose discoveries of microbes and vaccines had prevented all kinds of sickness and death. In 1888, Metchnikoff was given an appointment at Pasteur’s prestigious research institute, in Paris, where he worked until his death in 1916.
Given Metchnikoff’s life experiences, you can understand why he may have felt reverence and gratitude for science. This was the era, after all, when scientists like Metchnikoff and Pasteur and many others were figuring out how pathogens worked and, with that scientific understanding, developing methods to fight them off.
The premise of Metchnikoff’s The Nature of Man is underscored in its subtitle, “Studies in Optimistic Philosophy.” In it Metchnikoff explains his optimism not only about science’s ability to fight disease, but to ward off a much more menacing threat: aging.
The inevitable decline of aging, Metchnikoff notes, has long pushed people away from science and into the consoling hug of religion. He cites a 2,000-year-old sermon by the Buddha: “Behold, O monks, the holy truth as to suffering. Birth is suffering, old age is suffering, disease is suffering, and death is suffering.” And he notes the same fatalism in a slew of modern writings, from Ecclesiastes (“He that increaseth knowledge, increaseth sorrow”) to Shakespeare (“Conscience does make cowards of us all”), Jean-Jacques Rousseau (“Know O people that nature has desired to preserve you from science as a mother tries to snatch a dangerous weapon from the hands of a child”), and Ferdinand Brunetière (“Science is powerless to resolve the sole problems that are essential, that concern the origin of man, the rules for his conduct, and his future destiny”).
But Metchnikoff seems especially irked by fellow Russian Leo Tolstoy’s thoughts on the inadequacies of science — perhaps because Tolstoy also struggled with depression and suicidal thoughts. Here’s a long snippet from his A Confession, published in 1884, in which he describes how he was satisfied with science until he began feeling the decline of old age and the reality of his own death:
My question — that which at the age of fifty brought me to the verge of suicide — was the simplest of questions, lying in the soul of every man from the foolish child to the wisest elder: it was a question without an answer to which one cannot live, as I had found by experience. It was: “What will come of what I am doing today or shall do tomorrow? What will come of my whole life?”
Differently expressed, the question is: “Why should I live, why wish for anything, or do anything?” It can also be expressed thus: “Is there any meaning in my life that the inevitable death awaiting me does not destroy?”
… From early youth I had been interested in the abstract sciences, but later the mathematical and natural sciences attracted me, and until I put my question definitely to myself, until that question had itself grown up within me urgently demanding a decision, I contented myself with those counterfeit answers which science gives.
Now in the experimental sphere I said to myself: ‘Everything develops and differentiates itself, moving towards complexity and perfection, and there are laws directing this movement. You are a part of the whole. Having learnt as far as possible the whole, and having learnt the law of evolution, you will understand also your place in the whole and will know yourself.’ Ashamed as I am to confess it, there was a time when I seemed satisfied with that. It was just the time when I was myself becoming more complex and was developing. My muscles were growing and strengthening, my memory was being enriched, my capacity to think and understand was increasing, I was growing and developing; and feeling this growth in myself it was natural for me to think that such was the universal law in which I should find the solution of the question of my life.
But a time came when the growth within me ceased. I felt that I was not developing, but fading, my muscles were weakening, my teeth falling out, and I saw that the law not only did not explain anything to me, but that there never had been or could be such a law, and that I had taken for a law what I had found in myself at a certain period of my life. I regarded the definition of that law more strictly, and it became clear to me that there could be no law of endless development; it became clear that to say, ‘in infinite space and time everything develops, becomes more perfect and more complex, is differentiated’, is to say nothing at all. These are all words with no meaning, for in the infinite there is neither complex nor simple, neither forward nor backward, nor better or worse.
Science and rationality, Tolstoy continued, are what make life insufferable. The only way to survive is to give in to an irrational faith: “Whatever the faith may be, and whatever answers it may give, and to whomsoever it gives them, every such answer gives to the finite existence of man an infinite meaning, a meaning not destroyed by sufferings, deprivations, or death.”
Metchnikoff, an atheist, is unsurprisingly critical of this outlook. His book (spoiler alert) doesn’t give the answer to the inevitability of death, but it does offer some hope regarding life’s sufferings and deprivations. Just as science had begun to unravel the mechanisms of microbial disease, Metchnikoff argues, so could it find the biological underpinnings of aging. And if aging could be understood, then its painful manifestations could be slowed, or even stopped. Released of the pain of growing old, there’d be no reason for anyone to be fearful or pessimistic about life, no reason to want to leave this earth.
It turns out that Metchnikoff’s specific ideas about what causes aging didn’t pan out.* But his ultimate claim — that science can help more of us live longer, and with less pain — has proven true, as evidenced by the last century’s rise in life expectancy and the increasing numbers of very old people. Obviously, today’s scientists have not yet figured out how to dramatically slow or stop the aging process. But there’s no inherent reason to think they won’t get there eventually — just as Pasteur’s work on microbes paved the way for treatments for the tuberculosis and typhoid that struck Metchnikoff’s wives.
“Scientists are accustomed to exploring the unknown,” Kirkwood writes in Time of Our Lives. “It serves no useful purpose to pretend that the deep secrets of aging will come easily. But the more we learn, the more reliably we will be able to anticipate future discoveries.”
*Metchnikoff believed that aging was caused in part by the distribution of gut bacteria, which, he wrote, “contributes nothing to the well-being of man” and “is the source of many poisons harmful to the body.” He drank sour milk every day, claiming that the lactic acid it contained would kill harmful gut bacteria. Some thirty years later, inspired by Metchnikoff’s book, Japanese scientist Minoru Shirota created a drink, called Yakult, made of a cultured strain of lactic acid bacteria. It was the world’s first commercial probiotic.